Malaria is among the deadliest of tropical diseases. Every year, it kills about 2 million people, most of them children. Increased resistance of vectors and parasites to insecticides and drugs, and the absence of an effective vaccine, all emphasize the need for new approaches for malaria control. This proposal focuses on the mosquito midgut stages of parasite development and has two main objectives. First, we propose to generate a transgenic mosquito that secretes an anti- parasitic protein into the gut lumen following a blood meal. Initial experiments will a) assess the effectiveness of various gut-specific gene regulatory elements to drive expression and secretion of foreign proteins into the mosquito gut lumen and b) evaluate the ability of several anti- parasitic proteins (monoclonal antibody 4B7, magainins, cecropins) to block midgut stages of parasite development. The best promoter will be linked to DNA sequences encoding the most effective anti-parasitic protein and the resulting construct will be transformed into the mosquito germ line. These transgenic mosquitoes are expected to be refractory to Plasmodium development. The second aim is to investigate the molecular interactions that occur between the Plasmodium ookinete and the midgut epithelium. In search of genes encoding epithelial cell surface proteins, a cDNA expression library will be screened with antibodies prepared against epithelial cell membranes. Special attention will be devoted to genes differentially expressed in a type of midgut that is preferentially invaded by the parasite. Proteins from candidate genes will be functionally tested for interaction with Plasmodium ookinetes. The identification of Plasmodium midgut ligands may lead to additional approaches for blocking parasite development in the mosquito. The four components of this application are directed toward finding novel solutions for the control of malaria transmission. The project targets the gut stages of parasite development. Other projects in this application seek to 1) develop a transgenic Anopheles Gambiae, 2) target the hemocoel stages of parasite development and 3) investigate how resistance genes can be driven into mosquito populations.